Time Domain Reshuffling Of Optical OFDM Signals

Orthogonal frequency division multiplexing (OFDM) is applied in many new and emerginghigh-speed wired and wireless communication systems, because it allows high-speed datatransmission across a dispersive channel and makes symbol duration long. In OFDM signals, undercertain conditions cyclic prefix can completely elimiting the inter-symbol interference (ISI) casusdby multi-path propagation and inter-carrier interference. Moreover, it can not damage theorthogonality between subcarriers. However, system efficiency will be sacrificed if CP is too long.Therefore, shorter guard interval method is emerging. However in some circumstances, signals stillmay surpass the guard interval. Part of signal energy of an OFDM symbol will be lost andcontributed to emerging ISI and ICI. In order to reduce such lost signal energy, we should makesingnal energy concentrate in central part of an OFDM symbol. Therefore we first propose OFDMsignal time domain reshuffling methods in wireless communication system and incoherent opticalcommunication system respectively. This paper shows how time domain reshuffling of opticalOFDM signals can simply be achieved. It makes signal energy in both parts is very little and reducethe lost part caused by surpassing.OFDM signal time domain reshuffling methods are proposed by analyzing the differencebetween Fourier transform and discrete Fourier transform. The method can achieve rearrangementof time domain signals by processing OFDM frequency domain signals. It makes signal energycentralized in the central part of an OFDM frame and smallest at the both end. The method is easyto process and can antipate to decrease ISI caused by shorter guard interval of received signal. It issignificant to develop and design of optical OFDM system which can reduce guard interval andimprove efficiency.